The present invention relates to a fluorine-containing unsaturated carboxylic acid, a fluorine-containing polymer compound obtained by polymerization of the carboxylic acid, a negative-type resist composition containing the polymer compound, and a pattern forming process by using the resist composition.
Various devices such as semiconductor devices are required to have higher density and higher integration. In particular, a demand for a photolithography that makes microfabrication possible has become strict year to year. For producing a DRAM having an integration degree of 1G bits or more, it is necessary to have a processing technology of a minimum line width of 0.13 micrometers or less. In response to this, a photolithography using KrF excimer laser (248 nm) or ArF excimer laser (193 nm) is used. Furthermore, the development of a photolithography using F2 excimer laser (157 nm) is in progress for the purpose of forming finer patterns.
Hitherto, as a negative-type resist material used in the circuit pattern formation by i-ray or KrF excimer laser light (248 nm) as a light source, there has been a chemically amplified, negative-type resist composition containing a combination of acid generator, a resin (e.g., novolac resin and polyhydroxystyrene) soluble in alkali aqueous solution, and an amino resin (e.g., melamine resin and urea resin) (see Japanese Patent Examined Publication 8-3635 B and its corresponding European Patent Application Publication 0232972 A2).
As a negative-type resist composition used in exposure to ArF excimer laser having a shorter wavelength, there is a negative-type resist composition (see SPIE Advances in Resist Technology and Processing XIV, Vol. 3333, p. 417-424 (1998)) that contains a carboxyl-containing resin component improved in transparency to ArF excimer laser, a crosslinking agent having an alcoholic hydroxy group, and an acid generator. In this composition, the carboxyl group contained in the resin component reacts with the alcoholic hydroxy group of the crosslinking agent by an action of the acid from the acid generator, thereby changing the resin component from alkali-soluble to alkali-insoluble. In a negative-type resist of such composition, it is possible to form a negative-type pattern upon exposure as a result of the formation of an ester bond between the crosslinking agent and the resin component in the presence of acid. In the negative-type resist composition, it has been possible to adjust solubility by introducing a carboxyl group as a moiety for providing solubility function, but it has not been possible to decrease swelling at the same time.
As carboxylic acid compounds having a fluorine atom at α-position, 2-fluoro-phenylacetic acid and its esters (see Japanese Patent Application Publication 1-242551) and ethyl 2,2-difluoro-3-hydroxy-3-phenylpropionate (see Tetrahedron Letters, Vo. 25, No. 22, pp 2301-2302, 1984) are known.